The present invention is directed to improvements in the lubrication supply and return or scavenge system of marine or industrial gas turbine engines. The most common lubrication system in use today is of the dry sump type wherein lubricating oil is carried externally of the engine in a separate tank or reservoir. In a gas turbine engine, the bearing assemblies must be lubricated with oil, and heat from the engine parts must be absorbed and dissipated by the same oil. It is common practice to house the engine bearing assemblies in their own respective sumps. The major components of a dry sump lubrication system comprise a lubricating oil reservoir or tank, a supply pump for supplying lubricating oil from the reservoir to the bearing assembly sumps under pressure. A scavenge pump for removing lubricating oil from the bearing assembly sumps. The scavenge pump causes the return lubrication oil to pass through a heat exchange assembly, on its way to the tank or reservoir. The heat exchange assembly often puts the return lubrication oil in heat exchange with the jet fuel used by the engine. Fuel, on its way to the combustor, enters and passes through the heat exchanger at a much greater flow rate than the oil, so that large quantities of heat are absorbed from the oil by the fuel. Appropriate filter means are also included in the system to remove contaminants from the oil.
The system also includes the necessary lubrication and scavenge lines. Prior art practice has been to secure the lubrication and scavenge lines by clamps and brackets to the engine cases, frames, ducts and the like. The routing of these lines has been affected by the routing of other systems similarly mounted to the engine. Routing conflicts had to be resolved. A change in the other systems often required changes in the routing of the lubrication and scavenge lines. Since the lubrication and scavenge lines run from the pumps to the turbine rear frame, almost every change in the engine impacted the lubrication and scavenge system in some way. By the same token, location of the lubrication and scavenge system on-engine, also restricted the routing of other systems.
The routing of the lubrication and scavenge system on-engine also posed thermal stress problems. The lubrication and scavenge lines passed over the hot section of the engine and routing was complicated by thermal loops. In addition, high stresses sometimes required the use of more costly materials such as nickel-ferrous alloys.
When it was necessary to remove portions of the engine casings, this often required time consuming dismantling of portions at least of the lubrication and scavenge system.
The present invention is based upon the discovery that the above-noted problems can be eliminated if the lubricant and scavenge lines from the supply and scavenge pumps can be supported off-engine. To this end, those supply and scavenge lines which extend aft to the rear bearing assembly sump are mounted on a longitudinally extending tray. These lines are straight and rigid and are connected at the aft end of the tray to the appropriate ones of the rear bearing assembly sump supply and scavenge tubes. The tray mounted supply line is connected by a flexible hose to the output of the supply pump and by another flexible hose to the supply tube of the center bearing assembly sump. The two tray mounted scavenge lines from the rear bearing assembly sump are connected by flexible hoses to the scavenge pump. The two rigid center bearing assembly sump scavenge lines are connected by flexible hoses to the scavenge pump, the hoses being supported by a bracket on the forward end of the tray. The tray is so mounted on the engine as to be capable of thermal growth in the forward direction, which growth is additionally accommodated by the flexible hoses. In this way, the supply and scavenge lines of the lubrication system do not interfere with other systems mounted on the engine. Furthermore, the tray mounted scavenge and supply lines can be disconnected from the system by disconnecting seven tube connections. The tray, itself, can be removed by the removal of eight bolts. The thermal and dynamic properties of this arrangement are excellent with infinite life expectancy. The cost of the system is far less than on-engine routed systems. Assembly time is drastically reduced. Removal of casings from combustor section or the turbine section is greatly facilitated.